[RichardJ]

I missed the DRW in the first post and assumed he is talking about a C30 SRW (single rear wheel).

I used a '76 C30 SRW as a donor for my '67 C20 (GMC 2500 actually).
I disassembled both and selected individual parts. The C30 had a bigger sway bar. The C30 big block springs were too big for my C20 6cyl. I used all the brake lines, locating the combination valve under the radiator. Where the brake lines go through the frame, there is already a hole, but needs enlarged.
The bolt holes for the crossmember to the frame are mostly the same. One hole on each side needs drilled and one hole needs slightly elongated.